I run 4 cell oval so i dont know how much my opinion matters, But i will say oval racers tend to be more picky on brushes and motors.
The all time best all around brush is going to be the reedy 767's..
I also like the xxx brushes. I have a pair in one of my motors, and i have prolly 50 runs on them and they are still going strong.. wel worth the money spent..
Now finishline brushes i was not a fan of.. I had brushes from batch one which in my opinion sucked.. i got some from batch two and they were better but not as good as i liked.. i went to a race a few eeks ago and got a few of the batch three from a guy who runs for them.. he showed me how he builds the motor with them, and i Love them now..
I love the putnam bule green combo.. i dont like they only last one run.. In my expirience i only use them at big races where i dont ind throwing them out after a run.. Ive tried everyhing and they just dont pull as hard after the first run..
If you motor is properly geard and not abused you should easily get 20 runs out of any brushes.. Brushes that dont last or go bad are over heated .. as long as the brush keeps its original color you can clean the face or re serrate and use them again.. I know a few 19 turn guys who still use the orignal orion brushes.. Im sure everyone knows they have not been made for years.. A buddy of mine has a set he has had in 4 19 turn motors.. the brushes have outlasted the motors life.. he takes care of them and they seem to get better and better..